Indophenazines as catalysts in dye bleach baths for color photography



, Where the metallic silver is present.

Patented Feb. 3, 1953 INDOPHENAZINES AS CATALYSTS IN DYE BLEACH BATE-IS FOR COLOR PHOTOG- BAPHY Joseph S. Friedman, Johnson (Jity, N. Y., assignor to General Aniline c Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application July 22, 1950,

a Serial No. 175,467

l l (llaims. 1

This invention relates to a method of processing photographic color pictures and particularly to pyrrolinophenazines and in dophenazines as accelerators for dye bleach baths used in the production of dyestufi images from dyed silver images.

It is known that in the production of photographic dyestufi images from diffusely dyed photographic emulsions containing a silver image, the latter image must be treated with a bleach bath which decolorizes or bleaches the dyestuff present in the photographic layer in the areas The dyes, which are employed in the diffuse dyeing of the silver halide emulsion layer, are primarily azo dyes, although vat dyes and alizarines may also be employed. The bleaching or decolorization of the dyestuif is accomplished in a bleach bath in which there occurs a simultaneous decolorization of the dye with an oxidation of the metal image at the points where silver is present, i. e., the metallic silver is converted into a silver compound which may be removed subsequently by fixation in a solution of hypo, or dissolved in the dye bleach solution, such'as a strong alkali iodide or an alkali thiocyanate solution.

The bleach baths, employed in this process, have relatively low pHs and consist of an aqueous solution of a hydrohalic acid, such as hydrochloric, hydrobromic ,acid,.etc., containing an alkali halide, such as potassium iodide, ammonium chloride, or both. Such baths require a relatively long treatment time so as to destroy the dyestuii present in situ with the silver image. Long treatment in bleaching solutions of high acidity has the tendency to soften the gelatin of the photographic emulsion containing a silver image and a bleachable dye. In order to avoid these shortcomings, various organic compounds have been proposed as catalysts which, when added to the bleach bath, accelerate the action of saidbath and materially reduce thecbleaching time.

The most practical catalysts so far suggested are the azines, such as phenazine, 2:3-diaminophenazine, and the like. Although phenazine and its substituted products are efiective as accelerators, they are highly colored substances and are substantive to gelatin, i. e., leave a stain in the gelatin layer Which is difficult to remove, and, which seriously aliects the quality or" the final image.

The latter property with respect to substituted phenazines is due to the presence of polar substituents, such as OH, NHz, 3031-1, and COOH. This is an undesirable feature when dye masks are prepared in monopack film containing dye images of the azomethine or quinonimine type. Moreover, substituted phenazines can only be used in dye bleach baths containing mineral acids because if the concentration of the phenazine accelerator is increased above the prescribed amounts, a heavier stain in the gelatin layer is obtained. 1

I have discovered that pyrrolinophenazines and indophenazines, which include benzoindophenazines and naphthoindophenazines, although colored substances ranging from reddish-orange to yellow in color, are not substantive to gelatin, do not stain the gelatin layer, and do not afiect the quality of the final dye image. The pyrrolinophenazines and indophenazines, because of the absence of polar substituents, have no afiinity for gelatin, can be readily washed out of the treated film and hence much stronger concentrations can be used, with a concomitant reduction of acid concentration, and increase in pH. This is a desirable feature when dye masks are prepared in monopack film containing dye images of the azomethine and quinonimine type. Such images are bleached and destroyed by strong acids such as would be used in silver dye bleach processing. However, by increasing the concentration of catalyst to 0.500 gram per liter, the hydrochloric acid could be replaced by a weaker acid, such as acetic, propionic,.tartar ic, citric, boric, or sulfonic acid. The pH of the resultant bath is no longer so low as to destroy the azomethine dye irreversibly. A bath utilizing acetic acid instead of hydrochloric acid can, therefore, serve to prepare a dye mask in a monopack film processed by dye coupling procedures.

The pyrrolinophenazines, indophenazines, benzoindophenazines, and naphthophenazines, which for sake of simplicity will be referred to hereafter as indophenazines, are characterized by the following general formulae:

N N H and Indophenazine(Gindol[2,3-111quln0xa1i11e) N 1 0 Ha O\N NI) 2-methy1indophenazine (2-metl1y1-6- indolo [2,3-11] quinoxaline) 3-methylind0phenazine 3-metl1y1-6- indolo [2,3-b quinoxaline) Q-methylindophenazine 9-methyl-6- indolo [2,3-b1quin0xaline) boil) 9, l0r-benzoindophenazine 7-benz0 [e] quinoxalo [2,3-12] indole) 1,2-benz0indophenz1zino 2-cthpxyindophenazine(2-ethoxy-G- lndolo [2,3-b quinoxaline) -O CzHa 3-ethoxyiudophenazine 3-ethoxy-6 indolo [2,3-b]quin0xaline) N .CH3

N N O1 11 3-ehloro-2-methylindophenazine(3-ch10r0-2- methylindolo [2,3-11] quinoxaline) 2,3-dimethoxyindophenz1zine (2,3-dimeth oxy-G- indolo [2,3-1) quinoxaline) O-methoxyindophenazine (Q-methoxy-G- indolo 2,34) quinoxaline) 8,9-benzoindophenazine-G-benzo [f]quinoxalo [2,341 indole H 8,9-naphtl10ind0phe nazine (5-indolo [2,3-b] naphtho[2,3-g1quinoxaline) U (EL/O 9,10-naphthoindophenazine 8-napl1tho 2,3-0] quinoxalo [2,3-17] indole) OCH:

CIIaO- 2,3-dip11enyl-1-pyrr0lo[2,3-b1qui11oxaline S-phenyl-Z-tolyl-l-pyrrolo [2,3-b1quinoxaline The foregoing indophenazines are generally prepared by the condensation of substituted or unsubstituted isatin with o-phenylenediamine or homologs thereof by following the procedures described in Beilstein, vol. 26, 4th ed., 1937, pages 88-118.

All of the foregoing indophenazines exert a very strong catalytic action upon dye destruction in situ with metallic silver and may be employed not only in relatively weak water-soluble acids, such as acetic, propionic, tartaric, citric, boric, or aryl sulfonic acid, e. g., benzene disulfonic or naphthalene trisulfonic acid, but also in mineral acid bleach baths, such as, for example, hydrochloric, hydrobromic, hydroiodic, sulfuric, sulfamic or phosphoric acid with or without the presence of alkali halide, such as sodium or potassium bromide or iodide, sodium chloride, ammonium chloride, and the like. The concentration of the mineral acid to be employed is dependent upon the character of the gelatin constituting the photographic color emulsion layer or layers used for color film containing azo dyes. The concentration of the acid may range from 5 to 100 cc. per liter of dye bleach solution. For photographic film containing color formers for the production of azomethine and quinonimine dye images, the concentration of hydrohalic acid or acetic acid may range from 25 to 100 cc. per liter of dye bleach solution, and the pH of these solutions must be sumciently high to avoid the destruction of the azomethine and quinonimine dye images. A pH range from 2.0 to 4.0 is preferred.

Since the indophenazines are water-soluble yellow to reddish-orange dyestuffs, which do not stain the gelatin, the amount employed as catalysts is not at all critical. The higher the amount within practical limits, the greater the catalytic activity. An amount as small as 0.005 gram per liter of bleach solution will have an appreciable bleaching action on silver bearing images. For practical purposes, amounts ranging from 0.005 to 1 gram per liter to saturated solutions may be employed.

A film dyed uniformly with an azo dye containing a negative silver image will upon treatment with adye bleach solution containing as little as 0.005 gram of an indophenazine be acted on at those places where silver images are present. The action is destruction of the dye in accordance with the concentration of silver present. At a point where considerable silver exists, 1. e., in the shadows, the dye destruction will be complete. In the highlights where little or no silver is present, little or no dye will be destroyed. In

intermediate regions, the destruction will be partial and to the extent of silver density. By this means a dye image which is a negative rela tive to the silver image is formed. If a silver image is a negative, then the dye image will be a negative of a negative or a positive.

A multicolor film containing color formers for the production of azomethine and quinonimine dye images is bleached and destroyed by strong mineral acids, such as those used in silver dye bleach processing. However, by increasing the concentration of the indophenazine catalyst to approximately 0.5 gram per liter of dye bleach solution containing from 25 to 100 cc. of a weak acid, such as acetic acid, the pH of such a bath can be adjusted so that it is no longer sufliciently low to destroy the azomethine dye irreversibly. A dye bleach bath, therefore, utilizing a weak acid instead of a strong acid, such as hydrochloric acid, can serve to yield a dye mask in a monopack film processed by dye coupling procedures.

A red-sensitive silver halide emulsion containing Direct Sky Blue (C. I. #520) was coated on a film base, dried, exposed, developed and fixed by 6 the usual processing baths. The fixed film was treated for 10 to 15 minutes in a dye bleach bath of the following composition:

Potassium iodide grams 100 Hydrochloric acid (35%) cc 100 Indophenazine "grams" 0.005

Water to make 1 liter.

Complete bleaching of the cyan layer took place Within 10 minutes with the formation of a cyan dyestuff image.

Example II A green-sensitive silver halide emulsion containing Fast Acid Magenta (C. I. #30) was coated on a film base, dried, exposed, developed, and fixed by the usual processing baths. The fixed film was treated for 10 to 15 minutes in a dye bleach bath of the following composition:

Potassium iodide grams 100 Hydrochloric acid (35%) cc 100 Z-methylindophenadine -grams 0.005

Water to make 1 liter.

Complete bleaching of the magenta layer took place within 10 minutes with the formation of a magenta dyestuff image.

Example III A blue-sensitive silver halide emulsion containing diphenylbiguanide hydrochloride and Dianil Yellow (C. I. #630) was coated on a film base, dried, exposed, developed, and fixed by the usual processing baths. The fixed film was treated for 10 to 15 minutes in a dye bleach bath of the following composition:

Potassium iodide grams 100 Hydrochloric acid (35%) cc 100 2-ethoxyindophenazine grams 0.005

Water to make 1 liter.

Complete bleaching of the yellow layer took place within 10 minutes with the formation of a yellow dyestuff image.

Example IV A green-sensitive silver halide emulsion. containing diphenylbiguanide hydrochloride and Cotton Red (Schultz #448) was coated on a. glass plate, dried, sensitometrically exposed, developed and fixed by the usual processing baths. The fixed film was treated for 10 to 15 minutes in a dye bleach bath of the following composition:

' Grams Potassium iodide Glacial acetic acid 80 9,10-Benzoindophenazine 0.4

Water to make 1 liter.

Within 10 minutes a red-colored image with clear highlights was formed.

Example V acid) -3-stearyl-5 pyrazolone as a color former for the magenta image, Benzo Fast Yellow (C. 1., 1st ed., #349A) as an azo masking dye, and diphenylbiguanide hydrochloride as a precipitating agent for the azo dye is coated on top of the cyan layer. After drying, this layer has a density of 1.5 at maximum absorption. The magenta layer is followed by a yellow filter layer and a blue-sensitive silver halide emulsion layer containing 5 (4 stearylaminobenzoylacetamino) terephthalic acid as a non-diffusing color former for the yellow dye image.

After exposure and color'development for approximately minutes at 68 F. in the following color developer:

Grams Sodium hexametaphosphate 1 Sodium bisulfite 1 Q-diethylaminoaniline 3 Sodium carbonate (monohydrate) 60 Hydroxylamine hydrochloride 1 Potassium bromide 1.5

Water to make 1 liter.

At this stage, the film contains yellow dye plus silver negative images in the top layer, magenta dye plus silver negative images and a uniform yellow azo dye in the magenta layer, and cyan plus silver negative images plus a uniform reddish azo dye in the cyan layer. The excess developer is washed from the film and the film subjected to the action of a dye bleach bath of the following composition:

Potassium iodide "grams" 100 Acetic acid cc 100 Indophenazine grams 0.5

Water to make 1 liter.

The length of time the film is treated in the bleach bath is determined by the time required to bleach the azo dyes and generally will not be sufficient to convert all of the silver into silver salts. Therefore, a treatment with ferricyanide or copper chloride or bromide bleach bath is needed to convert the unused silver to a silver salt soluble in hypo. Following the latter bleaching treatment, the film is fixed and washed in the usual manner.

Example Vl Example V was repeated with the exception that the Brilliant Purpurine 10B in the red-sensitive layer was replaced b Orange TA (C. I. #374) and the Benzo Fast Yellow in the greensensitive layer was replaced by Light Fast Yellow (C. I. #640). The negative obtained after processing differs from that obtained in Example V by having in the bottom layer an orange positive masking image instead of a reddish one.

While the present invention has been described with reference to certain preferred procedures, materials, and uses, it is understood that the invention is not limited thereto, that numerous variations may be made in the procedure herein described, and that equivalent materials may be substituted. Thus, for example, other color formers and other primary aromatic amino color developing agents may be used. Similarly, azo dyes other than those specifically mentioned and utilized in the foregoing examples, may be bleached satisfactorily, provided they are or can be used in the preparation of multilayer color film in which, after exposure, the dye images are obtained by the silver dye bleach process. Several hundreds of such dyes are known and further reference to them or to their methods of preparation need not be mentioned herein. Accordingly, the scope of the invention is to be defined by the following claims.

I claim:

1. A dye bleach bath for producing a colored image in a photographic emulsion layer containing a bleachable azo dye and a silver image comprising an aqueous solution of an alkali halide selected from the class consistin of alkali metal and ammonium bromides, chlorides, and iodides, and an acid selected from the class consisting of mineral and water-soluble organic acids and an accelerating amount of an indophenazine selected from the class consisting of those of the following formulae:

and

ring system of the benzene, naphthalene, and

anthracene series.

2. A dye bleach bath according to claim 1 in V which the indophenazine is indophenaz'ine.

3. A dye bleach bath according to claim 1 in which the indophenazine is 2-methylindophenazine.

4. A dye bleach bath according to claim 1 in which the indophenazine is Z-ethoxyindop-henazine.

5. A dye bleach bath according to claim 1 in which the indophenazine is 9,10-benzoindophenazine.

6. A dye bleach bath according to claim 1 in which the indophenazine is 9,10-naphthoindo phenazine.

'7. A dye bleach bath for producing a colored image in a photographic emulsion layer containing a bleachable azo dye and a silver image com prising an aqueous solution of acetic acid and an accelerating amount of indop-henazine.

8. The process of producing a colored image in an exposed and developed photographic layer containing a silver image and a bleachable azo dye which comprises bleaching said layer in a bath comprising an aqueous solution of an alkali halide selected from the class consisting of alkali metal and ammonium bromides, chlorides, and iodides, and an acid selected from the class consisting of mineral and water-soluble organic acids and an accelerating amount of an indophenazine selected from the class consisting of those of the following formulae:

I z B N N H wherein R represents a monocyclic aryl hydrocarbon radical and Z and Z represent the atoms necessary to complete a carbocyclic aromatic ring system of the benzene, naphthalene, and anthracene series.

9. The process according to claim '7, in which the indophenazine is indophenazine.

10. The process according to claim 7, in which and REFERENCES CITED The following references are of record in the file of this patent:

Beilstein: Handbuch der Organische Chemie," 4th ed.. 1937, vol. 26, pp. 88-118. 

1. A DYE BLEACH BATH FOR PRODUCING A COLORED IMAGE IN A PHOTGRAPHIC EMULSION LAYRE CONTAINING A BLEACHABLE AZO DYE AND SILVER IMAGE COMPRISING AN AQUEOUS SOLUTION OF AN ALKALI HALIDE SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL AND AMMONIUM BROMIDES, CHLORIDE, AND IODIDES, AND AN ACID SELECTED FROM THE CLASS CONSISTING OF MINERAL AND WATER-SOLUBLE ORGANIC ACIDS AND AN ACCELERATING AMOUNT OF AN INDOPHENAZINE SELECTED FROM THE CLASS CONSISTING OF THOSE OF THE FOLLOWING FORMULAE: 